1. Field of Use
This invention relates generally to self-propelled soil stabilizer machines which employ a horizontal rotor for pulverizing and mixing soil and other materials it passes over. In particular, the invention relates to improved hydraulic motor means for driving the rotor, improved means for sensing load conditions on the rotor and for effecting changes in the speed of machines travel in response thereto, and improved means for maintaining and automatically returning the rotor to a preset depth.
1. Description of the Prior Art
Some self-propelled diesel-powered pneumatic-tired soil stabilizer machines employ a single heavy-duty horizontal rotor for pulverizing and mixing native and prescarified in-place soils or other materials (with or without additives) to stabilize and achieve a strong homogeneous base for road construction and similar work. Heretofore, the rotor was driven from a power source on the machine through a drive mechanism which typically included components such as an engine power take-off, a drive shaft, gear boxes, transmissions, differentials, clutches, jack axle shafts, sprockets and chain drives, stub shafts at each end of the rotor, and mechanical shear pins for overload protection. In such systems rotor speeds were usually fixed and dependent on engine speed. Overload and shock load conditions imposed on the rotor by submerged rocks, concrete blocks or the like resulted in breakage of the shear pins necessitating pin replacement or, sometimes, failure of one of the drive mechanism components. This resulted in machine damage and costly down-time. Furthermore, prior art machines of this type usually had either of two basic types of means for controlling the depth of rotor cut. One type, called a depth block or floating system type, depended on the position of the mixing box that is pulled and slides along the surface of the soil being processed. At each end of the rotor was a housing enclosing the chain drive to the top of which was attached a vertical bar. The bars contained several holes for pinning depth blocks in place. The blocks thus located would not allow the rotor to go below that position. The position of the rotor was controlled by a single acting hydraulic cylinder. The other type, known as an automatic electric type depth control system, used a cam, limit switches, and solenoid valves to control the rotor position. This latter type received electrical signals from the cam actuated limit switches to correct for or return the rotor to a set depth position. The cam was connected to the lifting arms that raise or lower the rotating drum. In both of the above systems the mechanism and rotor depth position indication means was located to the rear of the operator's station on the machine. The depth block system did not provide for consistent depth control since the rotor could float up and over hard areas. The electrical control system was subject to premature failure due to vibration and extremes of wet and dusty conditions.